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The problem is based on the way that julia distinguishes between singleton arrays and nx1 two-dimensional arrays. The optional argument zs for plot3D( xs, ys, zs=zs ) is not robust to these two different representations but the first two arguments xs, ys are.
Say a matrix of data is generated and three sets of points for plotting are extracted from the columns of the matrix:
mat = [ 1 4 7;2 5 8;3 6 9 ]
x = mat[ :,1 ]
y = mat[ :,2 ]
z = mat[ :,3 ]
Each vector x, y, z is a 3-element Array{Int64,1}. These can be plotted using:
using PyPlot
close( gcf() )
plot3D( x, y, zs=z )
display( gcf() )
However, say the matrix is transposed and the rows are spliced and transposed:
x = mat'[ 1,: ]'
y = mat'[ 2,: ]'
z = mat'[ 3,: ]'
Each vector is now a 3x1 Array{Int64,2} and plotting as above gives:
using PyPlot
close( gcf() )
plot3D( x, y, zs=z )
display( gcf() )
PyError (PyObject_Call) <type 'exceptions.ValueError'>
ValueError('could not broadcast input array from shape (3,1) into shape (3)',)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/backend_bases.py", line 2177, in print_figure
**kwargs)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/backends/backend_agg.py", line 509, in print_png
FigureCanvasAgg.draw(self)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/backends/backend_agg.py", line 455, in draw
self.figure.draw(self.renderer)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/artist.py", line 59, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/figure.py", line 1050, in draw
func(*args)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/mpl_toolkits/mplot3d/axes3d.py", line 275, in draw
Axes.draw(self, renderer)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/artist.py", line 59, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/matplotlib/axes/_base.py", line 2076, in draw
a.draw(renderer)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/mpl_toolkits/mplot3d/art3d.py", line 124, in draw
xs, ys, zs = proj3d.proj_transform(xs3d, ys3d, zs3d, renderer.M)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/mpl_toolkits/mplot3d/proj3d.py", line 198, in proj_transform
vec = vec_pad_ones(xs, ys, zs)
File "/Library/Python/2.7/site-packages/matplotlib-1.4.x-py2.7-macosx-10.9-intel.egg/mpl_toolkits/mplot3d/proj3d.py", line 187, in vec_pad_ones
vec = np.array([xs,ys,zs,np.ones(xs.shape)])
while loading In[16], in expression starting on line 4
in pyerr_check at /Users/user/.julia/v0.3/PyCall/src/exception.jl:58
in pycall at /Users/user/.julia/v0.3/PyCall/src/PyCall.jl:85
in fn at /Users/user/.julia/v0.3/PyCall/src/conversions.jl:181
in writemime at /Users/user/.julia/v0.3/pyplot/src/pyplot.jl:140
in base64 at base64.jl:125
in display_dict at /Users/user/.julia/v0.3/IJulia/src/execute_request.jl:30
in display at /Users/user/.julia/v0.3/IJulia/src/inline.jl:34
in display at multimedia.jl:150
Clearly Plot3D cannot handle this difference well. However, it turns out that the required arguments xs, ys are robust to this whereas zs is not. Using the 3x1 Array{Int64,2} vectors again:
using PyPlot
close( gcf() )
plot3D( x, y )
display( gcf() )
Works fine.
Sorry for the very contrived example but this caused me some confusion earlier!
Thanks
The text was updated successfully, but these errors were encountered:
Ideally, these bugs would be fixed upstream.... currently, Matplotlib is very inconsistent about accepting row vs. column vectors (some functions allow it, some don't), and PyPlot has to work around this.
I didn't implement any workarounds for keyword arguments yet, though. It should be straightforward.
@olaslett, I don't think that's going to happen. Unlike Matlab, Julia has 1d arrays (all arrays in Matlab are at least 2d). Unless Julia defines a separate Array type for row vectors, those will need to be 2d arrays.
The problem is based on the way that julia distinguishes between singleton arrays and nx1 two-dimensional arrays. The optional argument
zs
forplot3D( xs, ys, zs=zs )
is not robust to these two different representations but the first two argumentsxs, ys
are.Say a matrix of data is generated and three sets of points for plotting are extracted from the columns of the matrix:
Each vector
x, y, z
is a3-element Array{Int64,1}
. These can be plotted using:However, say the matrix is transposed and the rows are spliced and transposed:
Each vector is now a
3x1 Array{Int64,2}
and plotting as above gives:Clearly Plot3D cannot handle this difference well. However, it turns out that the required arguments
xs, ys
are robust to this whereaszs
is not. Using the3x1 Array{Int64,2}
vectors again:Works fine.
Sorry for the very contrived example but this caused me some confusion earlier!
Thanks
The text was updated successfully, but these errors were encountered: